pub const SBOX: [u8; 256] = [
    0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
    0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
    0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
    0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
    0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
    0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
    0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
    0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
    0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
    0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
    0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
    0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
    0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
    0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
    0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
    0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16,
];

pub const INV_SBOX: [u8; 256] = [
    0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
    0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
    0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
    0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
    0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
    0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
    0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
    0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
    0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
    0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
    0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
    0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
    0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
    0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
    0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
    0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d,
];

pub fn xor(state: &mut [u8; 16], key: &[u8; 16]) {
    for i in 0..16 {
        state[i] ^= key[i];
    }
}

pub fn sub_bytes(state: &mut [u8; 16]) {
    for i in 0..16 {
        state[i] = SBOX[state[i] as usize];
    }
}

pub fn inv_sub_bytes(state: &mut [u8; 16]) {
    for i in 0..16 {
        state[i] = INV_SBOX[state[i] as usize];
    }
}

pub fn shift_rows(state: &mut [u8; 16]) {
    let mut temp: u8;

    // Rotate first row 1 columns to left
    temp = state[0 * 4 + 1];
    state[0 * 4 + 1] = state[1 * 4 + 1];
    state[1 * 4 + 1] = state[2 * 4 + 1];
    state[2 * 4 + 1] = state[3 * 4 + 1];
    state[3 * 4 + 1] = temp;

    // Rotate second row 2 columns to left
    temp = state[0 * 4 + 2];
    state[0 * 4 + 2] = state[2 * 4 + 2];
    state[2 * 4 + 2] = temp;

    temp = state[1 * 4 + 2];
    state[1 * 4 + 2] = state[3 * 4 + 2];
    state[3 * 4 + 2] = temp;

    // Rotate third row 3 columns to left
    temp = state[0 * 4 + 3];
    state[0 * 4 + 3] = state[3 * 4 + 3];
    state[3 * 4 + 3] = state[2 * 4 + 3];
    state[2 * 4 + 3] = state[1 * 4 + 3];
    state[1 * 4 + 3] = temp;
}

pub fn inv_shift_rows(state: &mut [u8; 16]) {
    let mut temp: u8;

    // Rotate first row 1 columns to right
    temp = state[3 * 4 + 1];
    state[3 * 4 + 1] = state[2 * 4 + 1];
    state[2 * 4 + 1] = state[1 * 4 + 1];
    state[1 * 4 + 1] = state[0 * 4 + 1];
    state[0 * 4 + 1] = temp;

    // Rotate second row 2 columns to right
    temp = state[0 * 4 + 2];
    state[0 * 4 + 2] = state[2 * 4 + 2];
    state[2 * 4 + 2] = temp;

    temp = state[1 * 4 + 2];
    state[1 * 4 + 2] = state[3 * 4 + 2];
    state[3 * 4 + 2] = temp;

    // Rotate third row 3 columns to right
    temp = state[0 + 3];
    state[0 * 4 + 3] = state[1 * 4 + 3];
    state[1 * 4 + 3] = state[2 * 4 + 3];
    state[2 * 4 + 3] = state[3 * 4 + 3];
    state[3 * 4 + 3] = temp;
}

fn xtime(x: u8) -> u8 {
    // performs multiplication with 'x' (or "2") in GF 2^8
    return (x << 1) ^ (((x >> 7) & 1) * 0x1b);
}

fn gf_mul(x: u8, y: u8) -> u8 {
    // multiplies two numbers in GF 2^8
    return ((y & 1) * x)
        ^ ((y >> 1 & 1) * xtime(x))
        ^ ((y >> 2 & 1) * xtime(xtime(x)))
        ^ ((y >> 3 & 1) * xtime(xtime(xtime(x))))
        ^ ((y >> 4 & 1) * xtime(xtime(xtime(xtime(x)))));
}

pub fn mix_columns(state: &mut [u8; 16]) {
    let mut tmp: u8;
    let mut tm: u8;
    let mut t: u8;

    for i in 0..4 {
        t = state[i * 4 + 0];

        tmp = state[i * 4 + 0] ^ state[i * 4 + 1] ^ state[i * 4 + 2] ^ state[i * 4 + 3];

        tm = state[i * 4 + 0] ^ state[i * 4 + 1];
        tm = xtime(tm);
        state[i * 4 + 0] ^= tm ^ tmp;

        tm = state[i * 4 + 1] ^ state[i * 4 + 2];
        tm = xtime(tm);
        state[i * 4 + 1] ^= tm ^ tmp;

        tm = state[i * 4 + 2] ^ state[i * 4 + 3];
        tm = xtime(tm);
        state[i * 4 + 2] ^= tm ^ tmp;

        tm = state[i * 4 + 3] ^ t;
        tm = xtime(tm);
        state[i * 4 + 3] ^= tm ^ tmp;
    }
}

pub fn inv_mix_columns(state: &mut [u8; 16]) {
    let mut a: u8;
    let mut b: u8;
    let mut c: u8;
    let mut d: u8;

    for i in 0..4 {
        a = state[i * 4 + 0];
        b = state[i * 4 + 1];
        c = state[i * 4 + 2];
        d = state[i * 4 + 3];

        state[i * 4 + 0] = gf_mul(a, 0x0e) ^ gf_mul(b, 0x0b) ^ gf_mul(c, 0x0d) ^ gf_mul(d, 0x09);
        state[i * 4 + 1] = gf_mul(a, 0x09) ^ gf_mul(b, 0x0e) ^ gf_mul(c, 0x0b) ^ gf_mul(d, 0x0d);
        state[i * 4 + 2] = gf_mul(a, 0x0d) ^ gf_mul(b, 0x09) ^ gf_mul(c, 0x0e) ^ gf_mul(d, 0x0b);
        state[i * 4 + 3] = gf_mul(a, 0x0b) ^ gf_mul(b, 0x0d) ^ gf_mul(c, 0x09) ^ gf_mul(d, 0x0e);
    }
}
